In-line type accumulators eliminate noise and vibration caused by pressure variations in pipe systems used to convey pressurized liquids. The center of the accumulator resembles a pipe section called an inner tube which is connected in series with the liquid conveying system. Liquid which passes through this inner tube has access to a surrounding liquid chamber via a number of passages in the wall of the inner tube. This liquid chamber is separated from a gas chamber by a flexible bladder called an isolating member. Pressure variations occurring within the pipe system cause liquid to flow through the passages in the wall of the inner tube, causing the liquid chamber to expand or contract against the isolating member until the pressure inside the liquid chamber equals the pressure inside the gas chamber. The effect is to mitigate changes in pressure within the pipe system and to eliminate noise and vibration caused therefrom.
A heretofore known in-line type accumulator is shown in FIG. 9. A large number of communication holes 2 are drilled in the circumferential wall of an inner tube 1. Three to four axially directed guide frames 4 are provided in a liquid chamber 3 outside of the inner tube 1. Between the outside of the guide frames 4 and a pressure vessel 5 are provided a cylindrical isolating member 6 made of an elastic material such as rubber or the like and flange portions 14 at both ends of isolating member 6. Each flange portion is clamped between pressure vessel 5, a bladder cap 7 and a side plate 8 in order to fixedly secure isolating member 6. The gas chamber 9 outside isolating member 6 and the liquid chamber 3 inside isolating member 6 are thereby isolated from each other. At the inside ends of the bladder caps 7 are provided protectors 11 to prevent the end portions of isolating member 6 from becoming acutely deformed during contraction.
This in-line type accumulator is designed so that isolating member 6 experiences very little stretching. This means that the transverse cross-sectional circumference of isolating member 6 in its natural configuration is nearly equal to its transverse cross-sectional peripheral length in its deformed configuration during contraction, as supported by the outer surfaces of inner tube 1 and guide frames 4. The purpose of this design is to minimize tensile stress experienced by isolating member 6, thereby reducing fatigue and ultimate failure.
Liquid enters the accumulator of FIG. 9 through inlet 12. A wire net cylinder 13 prevents isolating member 6 from entering the communication holes 2.
When the isolating member 6 contracts, its central portion folds regularly over the guide frame 4 causing its transverse cross-section to take a star shape. This prevents fatigue failure in the central portion. Since groove sections 15 are present at both ends of the cylindrical central portion, contraction of the isolating member 6 will cause deformation strains such as bending and stretching to occur at both ends. Hence, each time the isolating member 6 contracts, irregular and acute creases arise at these end portions, eventually causing damage and rupture (See Japanese Pat. No. 909648).